The present invention relates to a tape counter which is mounted on a tape recorder to count and display the amount of run of the tape.
A tape recorder is usually provided with a tape counter. Such tape counter generally comprises a substantially U-shaped frame including a bottom plate and a pair of upright side plates projected in a manner to oppose each other from both ends of said bottom plate, digit wheels and a driving gear thereof axially mounted on a digit wheel shaft in a freely rotatable fashion, the digit wheel shaft being supported between said side plates, a zero resetting bracket member which is rotatably supported on a supporting shaft arranged parallel to said digit wheel shaft and which further has a heart-shaped cam lever for depressing a heart-shaped cam formed on the side of the digit wheels, a rotation carry pinion interposed between digit wheels rotatably mounted on the supporting shaft on said zero resetting bracket member and a motion transmitting pinion interposed between the lowest order digit wheel and the driving gear, a push button member which rotates said zero resetting bracket member to have the heart-shaped cam lever depress the heat-shaped cam and which frees the meshing of the driving gear with the pinions, a rotary shaft rotatably inserted in a bearing shell formed at a corner of the frame bottom plate, a worm to be engaged with the driving gear fixed on the upper part of said rotary shaft, and a pulley fixed on the lower part of the rotary shaft and connected to the tape driving source via a belt. This type of tape counters may be exemplified by the one disclosed in U.S. Pat. No. 4,197,452. The tape counter disclosed in the above patent achieves rationalization in assembling process and reduction in costs through making all component elements with plastic materials in an integrated form. For example, the above counter adopts a structure where on the frame bottom plate is integrally projected a bearing plate having a shaft hole with an open upper end, and a pin shaft is integrally projected on both sides of the zero resetting bracket member, thereby materializing the so-called one-touch assembling of component members for a zero resetting bracket. In prior art the digit wheels are assembled by inserting a digit wheel shaft into a frame through a hole bored on a side plate, mounting consecutively each digit wheel and a driving gear thereto and forcing an shaft end into the shaft hole on the side plate of the other side. Such assembling operation is quite troublesome and needs skill and experience. Further, in prior art those components elements such as digit wheels and pinions are molded with synthetic resin and, therefore, susceptible to dimentional changes by environmental changes, causing frequent disengagement. In order to prevent such disengagement, a coil spring to adjust the side play or the movement on the digit wheels in the axial direction is incorporated between the highest order digit wheel and the frame side plate. Since this coil spring is extremely small in size and easy to warp, the step to assemble this coil spring onto the digit wheel shaft presents a formidable difficulty. The tape counter disclosed in the above mentioned U.S. Pat. is not required to magnify the digits on the digit wheels for display because the size thereof is relatively large. However, as the size of a tape recorder has become smaller, the size of a tape counter has been minimized, necessitating a means to magnify digits on digit wheels for display. The tape recorder disclosed in U.S. Pat. No. 4,221,327 incorporates such structure. The tape counter is provided with a cover molded with transparent synthetic resin which can be assembled over a frame having a lens member integrally formed therewith. In a cover of this type which is assembled with a frame by engaging dowels projected on both sides with small holes bored on side plates, the position of the cover is determined by the side plates, presenting heretofore difficulties in aligning the center line of the lens mechanism with the reading line of the digit wheels in manufacturing process. The disalignment of the center line of the lens member from the reading line causes distortion on digits and further the light reflected on expanded portion makes the displayed digits on the counter hard to read. As the size of mechanism is getting smaller and smaller, larger magnification becomes necessary and a greater radius of curvature required, intensifying above mentioned defects of the prior art.